We plan to utilize the hamster model in which benzo(a)pyrene -Fe2O3 is instilled intratracheally to study DNA repair in the trachea. In this regard, we will determine the stability of benzo(a)pyrene (BP)-DNA adducts in trachea, the aralkylation pattern of LH-20 Sephadex of the deoxyribonucleoside-polycyclic hydrocarbon complexes and the DNA damage as assessed by an alkaline elution technique. As a final aspect of this study, we will determine the effects of vitamin A deficiency upon the above parameters. It is known that this deficiency greatly increases the polycyclic hydrocarbon-induced incidence of squamous cell carcinomas in these hamsters. It is hoped that these studies will shed some light upon the interrelationships between carcinogenesis, vitamin A deficiency and DNA repair.